General Presentation of Eurocode 7 on 'Geotechnical Design'

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FRANK, R. Ka8rWrJTr'J<;, E.N.P.C, raAAfa

ABSTRACT: Eurocode 7 on 'Geotechnical design' is now actively being implemented th roughout

Europe. Part 1 devoted to the 'General rules' has been published in 2004 and National Annexes
are presently being prepared (2006) for final implementation in the various European countries.
Part 2 on 'Ground investigation and testing' was formally voted positively early 2006 and will be
published soon. After describing shortly the history of the development of Eurocode 7 , the contents
of the two documents are given and some important aspects are described {characteristic values,
derived values, ULS verifications, SLS verifications and allowable movements of fou ndations).

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1. INTRODUCTION The Structural Eurocodes are design codes

for buildings and civil engineering works. They
The system of Structural Eurocodes includes are based on the Limit State Design (LSD)
10 following sets of standards (EN for approach used in conjunction with a partial
'European Norm') : factor method.
EN 1990 Eurocode: Basis of structural design Except for EN 1990, all E urocodes are
EN 1991 Eurocode 1: Actions on structures subdivided into several parts. Eurocodes 2, 3,
EN 1992 Eurocode 2: Design of concrete 4, 5, 6 and 9 are 'material' Eurocodes, i.e.
structures relevant to a given material. EN 1990 (Basis of
EN 1993 Eurocode 3: Design of steel design), Eurocode 1 (Actions), Eurocode 7
structures (Geotech-nical design) and Eurocode 8
EN 1994 Eurocode 4: Design of composite (Earthquake resistance) are relevant to all
steel and concrete structures types of construction, whatever the material.
EN 1995 Eurocode 5: Design of timber struc- Eurocode 7 should be used for all the
tures problems of interaction of structu res w ith the
EN 1996 Eurocode 6: Design of masonry ground (soils and rocks) , through foundations
struc-tures or retaining structures. It addresses not only
EN 1997 Eurocode 7: Geotechnical design buildings but also bridges and other civil
EN 1998 Eurocode 8: Design of structures for engineering works. It allows the calculation of
earthquake resistance the geotechnical actions on the structures, as
EN 1999 Eurocode 9: D esign of aluminium well the resistances of the ground submitted to
structures the actions from the structu res. It also g ives all

133
the prescriptions and ru les for good practice 1997, a positive vote for the conversion into an
required for properly conducting the EN. It was the recogn ition by CENffC 250 that
geotechnical aspect of a structura l project or, geotechnical design is unique and cannot be
more general ly speaking, a purely considered to be the same as other design
geotechnical project. practices needed in the construction industry.
Eurocode 7 consists of two parts: The models commonly used vary from one
EN 1997-1 Geotechnical design- Part 1: country to the other and cannot be harmonised
General rules (CEN, 2004) easily, simply because the geologies are
EN 1997-2 Geotechnical design- Part 2: different and form the rationale for the so-
Ground investigation and testing (CEN, 2006) called 'local traditions'... This recognition is
After describing shortly the history of the confirmed by a resolution taken by TC 250
development of Eurocode 7, and giving the (Resolution N 87, 1996): ' CENfTC 250 accepts
main contents of the two parts, the main the principle that ENV 1997-1 might be
concepts are described, without recalling all devoted exclusively to the fundamental rules of
the principles of LSD and of the partial factor geotechnical design and be supplemented by
method used. national standards' .
The work for the conversion of ENV 1997-1
2 HISTORY OF EUROCODE 7 AND into EN 1997-1 'Geotechnical design - Part 1:
IMPLEM ENTATION General rules' was performed from 1997 to
2003. The formal positive vote by CEN
The first Eurocode 7 Group, in charge of members was obtained early 2004 and CEN
drafting a European standard on geotechnical finally published Eurocode 7 - Part 1 (EN
design, was created in 1981. It was composed 1997-1) in November 2004 (CEN, 2004).
of representatives of the National Societies for Eurocode 7 originally consisted of two other
Geotechnical Engineering of the 10 countries Parts: Part 2, devoted to geotechnical design
forming the European Community at that time. assisted by laboratory testing and Part 3,
A first model code on general rules for devoted to geotechnical design assisted by
geotechnical design (corresponding to field (in situ) testing. The corresponding ENVs
Eurocode 7- Part 1) was published in 1990 (ENV 1997-2 and 1997-3) were drafted rather
(EC7, 1990). quickly, facing no serious controversy. They
In 1990, the task of drafting design codes were published in 1999 (CEN, 1999a and
for buildings and civil engineering works was 1999b) and, in 2001, the members of CEN
transferred to the Comite Europeen de voted positively for their conversion into a
Normalisation (CEN, European Committee for European Norm. During the conversion phase,
Standardization) and CENffC 250 (Technical the two documents were merged into the
Committee 250) in charge of all the 'Structural single document called 'Eurocode 7
Eurocodes' was created. In particular, SC 7, Geotechnical design - Part 2: Ground
Sub-Committee 7, is in charge of Eurocode 7 investigation and testing'. The formal positive
on 'Geotechnical design'. Note that CEN is vote was obtained in May 2006 and the
composed of the national standard bodies of a document wil l now be published soon by CEN
number of European countries (in February (CEN, 2006).
2006, 29 countries are members, i.e. 25 The publication of a Eurocode Part by each
countries of EU , plus 3 countries of EFTA, plus national standardisation body with its National
Romania; 5 countries are affiliates). N. Krebs Annex (in the official language(s) of the
Ovesen (Denmark) was the first Chairman of country) has to be completed within two years
CENffC 250/SC 7, from 1990 until 1998. The after publication by GEN. The role of the
author was the Chairman of SC 7 from 1998 to National Annex is to indicate the decisions
2004. Since June 2004, Bernd Schuppener co rresponding to the so-called "Nationally
(Germany) is the new Chairman. Determined Parameters (NDPs)". The National
In 1993, SC 7 adopted the ENV 1997-1 pre- An nex can also give a 'normative' status to one
standard: 'Geotechnical design - Part 1: or to several of the 'informative' Annexes, i.e. it
General Rules' (CEN, 1994). It was clear, at (they) will be mandatory in the corresponding
that time, that (much) more work still needed to country.
be done before reaching a full European As mentioned above, each country is also
standard (EN) acceptable to all members of free to supplement the general rules of
GEN. An important fact helped in obtaining, in Eurocode 7 by national application standards,

134
in order to specify the calculation models and Annex C Sample procedures to determine
design rules to be applied in the country. limit values of earth pressures on vertical walls
Whatever their contents they will have to Annex D A sample analytical method for
respect in all aspects the principles of bearing resistance calculation
Eurocode 7. Annex E A sample semi-empirical method
for beanng resistance estimation
3 CONTENTS OF DOCUMENTS Annex F Sample methods fo r settlement
evaluation
3.1 Part 1: General rules Annex G A sample method for deriving
presumed bearing resistance for spread
Eurocode 7 - Part 1 is a rather general foundations on rock
document giving only the principles for Annex H Limiting foundation movements
geotechnical design inside the general and structural deformation
framework of LSD. These principles are Annex J Checklist for construction
relevant to the calculation of the geotechnical supervision and performance monitoring
actions on structures {buildings and civil Annex A is important, as it gives the partial
engineering works) and to the design of the factors for ULS in persistent and transient
structural elements themselves in contact with design situations (fundamental combinations),
the ground (footings, piles, basement walls, as well as correlation factors for the
etc.). Detailed design rules or calculation characteristic values of pile bearing capacity.
models, i.e. precise formu lae or charts are only But the numerical values for the partial or
given in informative Annexes. As already correlation factors given in Annex A are only
mentioned, the main reason is that the design recommended values. The exact values of the
models in geotechnical engineering differ from factors can be changed by each national
one country to the other, and it was not standardisation body in the so-called National
possible to reach a consensus, especially Annex. All other Annexes are informative (i. e.
when many of these models still need to be not mandatory in the normative sense). Some
calibrated and adapted to the LSD approach ... of them , though, contain valuable material
Eurocode 7 - Part 1 includes the following which can be accepted, in the near future, by
sections (CEN, 2004) : most of the countries. The National Annex can
Section 1 General give a 'normative(s)' status to one or to several
Section 2 Basis of geotechnical design of the 'informative' Annexes, i.e. it (they) will be
Section 3 Geotechnical data mandatory in the corresponding country.
Section 4 Supervision of construction, The national application standards,
monitoring and maintenance specifying the calculation models and design
Section 5 Fill, dewatering, ground rules to be applied in the country, will also
improvement and reinforcement depend on the choices made with regard to the
Section 6 Spread foundations application of the informative Annexes of
Section 7 Pile foundations Eurocode 7.
Section 8 Anchorages
Section 9 Retaining structures 3.2 Part 2: Ground investigation and testing
Section 10 Hydraulic failure
Section 11 Overall stability The role of this part of Eurocode 7 devoted to
Section 12 Embankments laboratory and field testing is to give the
Sections 8 on anchorages, 10 on hyd raulic essential requirements for the equipment and
failure and 11 on site stability are new sections test procedures, for the reporting and the
with regard to the pre-standard (ENV 1997-1, presentation of results , for their interpretation
CEN, 1994). and, finally, for the derivation of values of
A number of Annexes are included. They geotechnical parameters for the design. It
are all informative, except for Annex A which is complements the requirements of Part 1 in
'normative' (i. e. mandatory). The list of the order to ensure a safe and economic
Annexes for EN 1997-1 is the following: geotechnical design.
Annex A (normative) Partial factors for It makes the link between the design
ultimate limit states requirements of Part 1, in particular Section 3
Annex B Background information on partial 'Geotechnical data', and the results of a
factors for Design Approaches 1, 2 3 number of laboratory and field tests.

135
 It does not cover the standardisation of the As is the case in Part 1, most of the
geotechnical tests themselves. Another derivations or calculation models given are
Technical Committee (TC) on 'Geotechnical informative, but there is also fairly good
investigation and testing' has precisely been agreement about using them in the future
created by CEN to consider this matter (TC throughout Europe. In any case, they are a
341). In this respect the role of Part 2 of clear picture of the approaches existing on the
Eurocode 7 is to 'use' and refer to the detailed continent for the use of in situ or laboratory test
rules for test standards covered by TC 341 . results in the design of geotechnical structures.
Eurocode 7 - Part 2 includes the following
Sections (CEN, 2006): 4 SOME ASPECTS OF EUROCODE 7
Section 1 - General
Section 2 - Planning of ground investi· 4.1 Characteristic values
gations
Section 3 - Soil and rock sampling and The present 'philosophy' with regard to the
groundwater measurements definition of characteristic values of
Section 4 - Field tests in soils and rocks geotechnical parameters is contained in the
Section 5 - Laboratory tests on soils and following clauses of Eurocode 7 - Part 1
rocks (clause 2.4.5.2 in EN1997- 1):
Section 6 - Ground investigation report ' (2)P The characteristic value of a
The Section on field tests in soils and rocks geotechnical parameter shall be selected as a
includes: cautious estimate of the value affecting the
• cone penetration tests CPT(U) occurrence of the limit state.'
· pressuremeter tests PMT '(7) {. .. }the governing parameter is often the
· rock dilatometer tests ROT mean of a range of values covering a large
• standard penetration tests SPT surface or volume of the ground. The
• dynamic penetration tests DP characteristic value should be a cautious
• weight sounding tests WST estimate of this mean value.'
· field vane tests FVT These paragraphs in Eurocode 7 - Part 1
- flat dilatometer tests DMT reflect the concern that one should be able to
• plate loading tests PLT keep using the values of the geotechnical
The Section on laboratory testing of soils parameters that were traditionally used {the
and rocks deals with: determination of wh ich is not standardised, i.e.
· preparation of soil specimens for testing they often depend on the individual judgment
• preparation of rock specimens for testing of the geotechnical engineer, one should
· tests for classification, identification and confess). However two remarks should be
description of soils made at this point: on the one hand, the
• chemical testing of soils and groundwater concept of 'derived value' of a geotechnical
• strength index testing of soils parameter (preceding the determination of the
• strength testing of soils characteri stic value), has been introduced (see
- compressibility and deformation testing of paragraph 4.3) and, on the other hand, there is
soils now a clear reference to the limit state involved
· compaction testing of soils (which may look evident, but is, in any case, a
· permeability testing of soils way of linking traditional geotechnical
- tests for classification of rocks engineering and the new limit state approach)
· swelling testing of rock material and to the assessment of the mean value (and
· strength testing of rock material not a local val ue; this might appear to be a
There are provisions on how to establish specific feature of geotechnical design which,
and use the so-called 'derived values' from the indeed, involves 'large' areas or 'large' ground
tests (see paragraph 4.3 below). Some of masses).
these provisions are meant to give guidance Statistical methods are mentioned only as a
for using the sample calculation models in the possibility:
Annexes of Part 1. Part 2 also includes a '(10) If statistical methods are employed
number of informative Annexes with precise {. .. ], such methods should differentiate
examples of derived values of geotechnical between local and regional sampling{. . .}.'
parameters and coefficients used commonly in '(11) If statistical methods are used, the
design. characteristic value should be derived such

136
that the calculated probability of a worse value f\p:VIIN
I rlC'Io.JI t..t.. ona. ....
governing the occurrence of the limit state
under consideration is not greater than 5%. IMHmwltowt
NOTE In this respect, a cautious estimate of the I ~~ ~ulh 1111\d
humtllhrr

mean value is a selection of the mean value of the dcri,cd Hllu.-..

limited set of geotechnical parameter values, with a

confidence level of 95%; where local failure is
concerned, a cautious estimate of the low value is a
5% fractile.'
The general feeling is that the characteristic
value of a geotechnical parameter cannot be
fundamentally different from the value that was
traditionally used. Indeed , for the majority of
projects, the geotechnical investigation is such
that no serious statistical treatment of the data
can be performed. Statistical methods are, of
course, useful for very large projects where the
amount of data justifies them. Figure 1. General framework for the selection
of derived values, characteristic values and
4.2 Derived values design values of geotechnical properties (CEN,
2006)
Many geotechnical tests, particularly field LXr'liJO 1. r £vtK6 TTAOiO'tO yta TrJV £TTtAoy~ TWV
tests, do not allow basic geotechnical TTOpaywywv ~£y£9ti.Jv , TWV XOPOKTilPIOTIKWV
parameters or coefficients, for example for TI~WV KOI TWV TI ~ WV OX£0100 ~ 0U TWV
strength and deformation, to be determined V£WT£XVIKWV IOIOT~TWV (CEN, 2006)
directly. Instead, values of these parameters
and coefficients must be derived using '(1)P Where relevant, it shall be verified that
theoretical or empirical correlations. the following limit states are not exceeded:
Derived values of a geotechnical parameter - Joss of equilibrium of the structure or the
then serve as input for assessing the ground, considered as a rigid body, in which
characteristic value of this parameter in the the strengths of structural materials and the
sense of Eurocode 7 - Part 1 (clause 2 .4.5.2 of ground are insignificant in p roviding resistance
EN 1997-1) and, further, its design value, by (EQU);
applying the partial factor 'YM ('material factor', - internal failure or excessive deformation
clause 2.4.6.2). of the structure or structural elements
The role played by the derived values of including footings, piles, basement walls, etc.:
geotechnical parameters can be understood in which the strength of structural materials is
with the help of figure 1, taken from Eurocode significant in providing resistance (STR);
7 - Part 2. The borderline between Part 1 (EN - failure or excessive deformation of the
1997-1) and Part 2 (EN 1997-2) of Eurocode 7 ground, in which the strength of soil or rock is
is also shown on the figure. It can be seen that significant in providing resistance (GEO);
the requirements concerning the - Joss of equilibrium of the structure or the
measurements of geotechnical properties, as ground due to uplift by water pressure
well as their derived values are covered by (buoyancy) or other vertical actions (UPL);
Part 2: 'G round investigation and testing', while - hydraulic heave, internal erosion and
those concerning the determination of piping in the ground caused by hydraulic
characteristic values and design values are gradients (HYD).
given by Part 1: 'General rules'. NOTE Limit state GEO ts often critical to the sizmg
of structural elements mvolved in foundations or
retaining structures and sometimes to the strength
4.3 ULS verifications
of structural elements.'
The ultimate limit states should be verified
The ultimate limit states (ULS) to be checked
for the combinations of actions corresponding
are defined, in the following manner, by
to the following design situations (see EN
Eurocode 7 - Part 1, consistently with
1990, CEN, 2002):
'Eurocode: Basis of structural design' (CEN
permanent and transient (the
2002) (clause 2.4.7.1 in EN 1997-1 ):
corresponding combinations are called

137
 'fundamental'); in the following these design values given may be modified by National
situations are noted 'p&tds' for convenience; decision.
accidental;
seismic (see also Eurocode 8 - Part 5, i.e. Table 1. Recommended values for partial
EN 1998-5). factors for actions (Set A) after EN 1990 (CEN,
The design values of the actions and the 2002)- ULS in p&tds
combinations of actions are defined in EN niVOKO<; 1. LUVIOIW~EVE<; TI~E<; TWV ElTI~tpou<;
1990 (partial factors y for the actions and OUVTEAEOTWV VIO Tl<; 6p60EI<; (Set A) OTT6 EN
factors IV for the accompanying variable 1990 (CEN , 2002) - ULS OE ~OVI~E<; KOI
actions). np6oKOIPES KOTOOIOOEIS OXE61oo~ou
The debate about the format for checking Aclion Symbol Value
Permanent actions
the GEO and STR ultimate limit states (ULS)
- unfavourable
was relevant to the persistent and transient - favourable
design situations ('p&tds'). This debate follows Variable actions
from the ENV 1997-1 (CEN, 1994) formulation - unfavourable 'to 1.50
which inferred that ULS in persistent and - favourable 0
transient design situations had to be checked (1)As an alternative, the lavourable part may be
multiplied by YG .,, = 1 15 and the unfavourable part by
for two formats of combinations of actions, i.e.
Gs = 1.35
for Cases 8 and C, as they were called at that
time. 8 was aimed at checking the uncertainty
Table 2. Recommended values for partial
on the loads coming from the structure, and C
factors for actions (Set 8) after EN 1990 (CEN,
the uncertainty on the resistance of the
2002)- ULS in p&tds
ground. Some geotechnical engineers were in
niVOKO<; 2. LU VIOTW ~ EVE<; TI~E<; TWV ElTI~tpou<;
favour of th is double check , as others
ouvrEA.wrwv y1o 11<; 6p60EI<; (Set B) on6 EN
preferred having to use only one single format
1990 (CEN, 2002) - ULS OE IJOVIIJE<; KOI
of combinations of actions (more details can
np6oKOIPES Koroar6oEIS oxE6IOOIJOU
be found in Frank and Magnan, 1999).
Act1on Svmbol Value
The consensus reached between structural Eq. Eq. Eq.
and geotechnical engineers opened the way to (6.10) (6.1 Oal (6.1Obi
three different Design Approaches (DA 1, DA 2 Permanent
and DA 3). The choice is left to national -unfavourable10 Jt;sup 1.35 1.35 1 15121
determination, i.e. each country wi ll have to - favourable1' 1 Jt;onl 1.00 1.00 1.00
state in its National Annex, the Design Variable
- unfavourable Yo 1.50 1.5ljlo 1.50
Approach(es) to be used for each type of - favourable 0 0 0
geotechnical structure (spread foundations, (1) all permanent act1ons from one source are mu1t1phed
pile foundations, retaining structures, slope by YGsup or by YGonl·
stability). =
(2) value of 1; is 0.85, so that 0.85YGsuo 0.85 x 1.35 =
Generally speaking, for checking ULS- 1.15.
Note 1 : choice between expression 6. 10 or expressions
p&tds, three sets of partial factors to be
6.1Oa and 6.1Ob used together, IS by National decision
applied to characteristic values of actions are .Note 2: YG and Yo may be subdivided into Yg and yq and
introduced in EN 1990: Sets A, 8 , and C: the model uncertainty factor YSd· YSd =
1.15 is
- set A is used for checking the static recommended.
equilibrium of the structure (EQU);
- set 8 is relevant to the design of Table 3. Recommended values for partial
structural members (STR) not involving factors for actions (Set C) after EN 1990 (CEN,
geotechnical actions; 2002) - ULS in p&tds
- sets 8 and C are relevant to the design nivOKO<; 3. LUVIOIWIJEVE<; TI~E<; TWV ElTIIJEPOU<;
of structural members involving geotechnical ouvrEA.Earwv y1o 11<; 6p6oEI<; (Set C) orr6 EN
actions and the resistance of the ground 1990 (CEN , 2002) - ULS OE ~OVI~E<; KOI
(STR/GEO) . rrp6oKOIPES KOTOOTOOEIS OXEOiao~ou
Tables 1, 2 and 3 give, in a simplified Action Symbol Value
manner, the recommended values for Permanent actions
- unfavourable 1.00
buildings for Sets A, 8 and C, taken from - favourable 1.00
Tables A 1.2 (A), A 1.2(8) and A 1.2(C) of Vanable actions
EN 1990 (CEN, 2002). The recommended - unfavourable Yo 1.30
- favourable 0

138
 For STRJGEO ULS in p&tds, the three Annex A also gives recommended values for
Design Approaches are the following {clause the partial factors; these values may be set
A1 .3. 1 in EN 1990): differently by the National Annex. Note that the
'(5) Design of structural members (footings, recommended values for the partial factors YM
piles, basement walls, etc.) (STR) involving on material properties in Set M1 are always
geotechnical actions and the resistance of the equal to 1.0.
ground (GEO) should be verified using one of
the following three approaches supplemented, Table 4. STR/GEO - ULS in p&tds. Partial
for geotechnical actions and resistances, by factors to be used according to EN 1990 and
EN 1997: EN 1997-1
Approach 1: Applymg in separate nivaKac; 4. STR/GEO - ULS 0£ iJOVIiJ£<:; KOI
calculations design values from Table A 1.2(C) np60K01p£c; KOTOOT00£1<:; OX£5IOOiJOU. 0 1
and Table A 1.2(8) to the geotechnical actions ETIIiJtpouc; ouvre:.>.£ortc; va XPilOiiJOTI011l80uv
as well as the other actions on/from the OU iJq>WVO IJ£ TO EN 1990 KOI EN 1997 1 -
structure. In common cases, the sizing of Design Actions on/from Geotechnical
foundations is governed by Table A 1.2{C) and Approach the structure
Actions Resistances
the structural resistance IS governed by Table
A1.2(8); B Band M1 M1 and R1
Note: In some cases, applicatiOn of these tables 1s 1
more complex, see EN 1997. M2 and R1
Approach 2: Applying design values from
c C and M2 or
M1 and R4'
Table A 1.2(8) to the geotechnical actions as 2 B Band M1 M1 and R2
well as the other actions on/from the structure; 3 B C and M2 M2 and R3
Approach 3: Applying design values from for p11es and anchorages
Table A 1.2(C) to the geotechnical actions and,
simultaneously, applying partial factors from In DA 1, the first format (combination 1,
Table A 1.2(8) to the other actions on/from the former case B) applies safety mainly on
structure. actions, while the factors on resistances have
Note: The use of approaches 1, 2 or 3 is chosen m recommended values equal to 1.0 (Sets M1
the National annex.' and R1) or near 1.0 (Set R1 in the case of
In other words, Design Approach 1 (DA 1) is axially loaded piles and anchorages); in the
th e double check procedure coming from the second format imposed by DA 1
ENV 1997-1 (B+C verification) and Design (combination 2, former case C), the
Approaches 2 (DA 2) and 3 (DA 3) are new elementary properties of the ground (shear
procedures using a single format of strength parameters) a re always factored for
combinations of actions. DA 2 is elaborated the calculation of geotechnical actions and
with 'resistance factors' for the ground (RFA), sometimes factored for the calculation of
as DA 3 makes uses of 'material factors' for resistances (Set M2) ; in the case of axially
the ground (M FA). loaded piles and anchorages, the total
Furthermore, Eurocode 7 allows to apply resistance is directly factored by applying
the partial factors either on the actions Set R4.
themselves ("at the source") or on the effects In DA 2 , safety is applied both on the
of the actions (they are noted YF and YE, actions (Set B) and on the total ground
respectively). In principle, for DA 1 they are resistance (Set R2).
applied "at the source". For DA 2 and DA 3, In OA 3, safety is applied both on the
both options are allowed. This is relevant to actions (Set B for the actions coming from the
the factors of set B and of set C (unfavourable structure and Set M2 for the elementary
variable actions). properties of the ground acting on the
Table 4 gives the link between Sets B and structure, i.e. for the geotechnical actions) and
C and the corresponding sets of factors for on the geotechnical resistances (Set M2 for
geotechnical actions and resistances: Sets M1 the elementary properties; the recommended
and M2 for material properties (e.g. c', q>', cu. values for Set R3 for the total geotechnical
etc.) and Sets R1 , R2, R3 and R4 for total resistance is always equal to 1 .0, except for
resistances (e.g. bearing capacity, etc.). piles in tension and anchorages for which they
These sets are defined in Annex A of are equal to 1.1) .
Eurocode 7 - Part 1. As mentioned above,

139
 More details on the use of the three Design with Ed the design value of the effect of actions
Approaches are given, for instance, in Frank et and cd the limiting value (serviceability
al. (2004). criterion) of the design value of effect of
With regard to the design values for actions.
accidental situations, Eurocode 7 only states Paragraph (2) applies to the actions in the
that (clause 2.4.7.1 in EN 1997-1): characteristic, frequent or quasi-permanent
'{3) All values of partial factors for actions or combinations (see EN 1990), as well as to the
the effects of actions in accidental situations geotechnical properties, such as the modulus
should normally be taken equal to 1,0. All of deformation. It should be noted that, for
values of partial factors for resistances should determining the differential settlement for
then be selected according to the particular instance, sets of lower characteristic values
circumstances of the accidental situation. and upper characteristic values can be chosen
NOTE The values of the parllal factors may be set in order to take account of the ground
by the National annex.' variability.
The last general paragraph in Eurocode 7 -
4.4 Verification of serviceability limit states Part 1 about SLS states that (clause 2.4.8 in
(SLS) EN 1997-1):
'(S)P A limiting value for a particular
The main discussions during the development deformation is the value at which a
of Eurocode 7 were about the format for serviceability limit state, such as unacceptable
verifying ULS in permanent and transient cracking or jamming of doors, is deemed to
situations. However, the verification of occur in the supported structure. This limiting
serviceability limit states (SLS) is an issue value shall be agreed during the design of the
equally important in contemporary supported structure.'
geotechnical design. This issue is fully The application of these general clauses is
recognised by Eurocode 7 which indeed often detailed further down in Eurocode 7 - Part 1
refers to displacement calculations of for each geotechnical structure (in the Sections
foundations and retaining structures, while for spread foundations, pile foundations,
common geotechnical practice mainly sought retaining structures, overall stability and
so far to master serviceability by limiting the embankments). It is interesting to note that the
bearing capacity or by limiting the shear document insists several times on the difficulty
strength mobilisation of the ground to relatively to predict displacements with accuracy (in the
low values. present state of geotechnical engineering
The verification of SLS in the real sense knowledge, of course!) .
proposed by Eurocode 7 (prediction of
displacements of foundations) is certainly 4.5 Limiting values of displacements of
going to gain importance in the near future . For foundations
the time being, it is an aspect which is too
often neglected in common geotechnical The knowledge of limiting allowable
practice. displacements of foundations is a subject of
Eurocode 7 - Part 1 repeats the formula- prime importance, even though it is not often
tion of EN 1990 (clause 2.4 .8, EN 1997-1): explicitly addressed. These limiting values
'(1 )P Verification for serviceability limit depend primarily, of course, on the nature of
states in the ground or in a structural section, the supported structure, but it has also been a
element or connection, shall either require that: point of interest for geotechnical engineering
for a long time, as well (a summary of data
collected for buildings and bridges is given e.g.
by Frank, 1991 ).
or be done through the method given in The limiting values of movements of
2.4.8(4). foundations is the subject , in particular, of
{2) Values of partial factors for serviceability clause 2.4.9, as well as of Annex H
limit states should normally be taken equal (informative) of Eurocode 7- Part 1. It is noted
to 1,0. that clause 2.4.9 contains 4 rather strong
NOTE The values of the partial factors may be set principles, i.e. paragraphs (1 )P to (4)P. The
by the National annex. ' first one says:

140
 '(1)P In foundation design, limiting values A B C 0
shall be established for the foundation
movements. NOTE Permitted foundation
movements may be set by the National annex.'
Furthermore, it seems that not only SLS
are concerned (see above) but also
ULS ... (because movements of foundations
can trigger an ULS in the supported structure).
Eurocode 7 gives a list of a certain number
of factors which should be considered when
establishing the limiting values of movements.
It is important that these limiting values are

~
established in a realistic manner, by close
collaboration between the geotechnical

~
engineer and the structu ral engineer. If the
values are too much severe, they will usually
lead to uneconomical designs.
Figure 2 defines the parameters used to
quantify movements and deformations of
structures. This figure , originally due to
Burland and Wroth (1975) is reproduced in
Annex H (informative) of Eurocode 7- Part 1.
Annex H quotes the following limits after
Burland et al. (1977):
- for open framed structures, infilled frames
and load bearing or continuous brick walls:
maximum relative rotations between about
1/2000 an about 1/300 to prevent the a) definitions of settlement s, differential
occurrence of a SLS in the structure; settlement os, rotation 8 and angular strain
- for many structures, a maximum relative a
rotation 13 = 1/500 is acceptable for SLS and b) definitions of relative deflection Ll and
13 = 1/150 for ULS; deflection ratio Ll!L
- for normal structures with isolated c) definitions of tilt w and relative rotation
foundations, total settlements up to 50 mm are (angular distortion) f3
often acceptable.
These values can serve as a guide, in the Figure 2. Definitions of foundation movements
absence of other indications on the limiting and deformations of structures (CEN, 2004,
values for the deformations of the structures. after Burland and Wroth, 1975)
LX~IJO 2. OpiO"IJO[ TWV IJETOKIV~O"EWV TWV

5 LIAISONS WITH OTHER CEN AND ISO 8E1JEAIWO"EWV KOI TTOPOIJOP<pWO"EWV TWV
COMMITTEES KOTOO"KEUWV (CEN , 2004, OTTO Burland KOI
Wroth, 1975)
Inside the Eurocode system itself, there are,
of course, many links between the different The other Technical Committees of CEN
standards or parts of them. Eurocode 7 on working on standards of interest for Eurocode
Geotechnical design is more precisely linked to 7, and for which coordination must be ensured
the following ones: are: CEN/TC 341 on 'Geotechnical investiga-
- EN 1990: 'Eurocode: Basis of structural tion and testing', as mentioned earl ier;
design' which defines the various limit states CEN/TC 288 on 'Execution of geotechnical
and design situations to be checked, and gives works'; CEN/TC 189 on 'Geotextiles and
the general rules for taking into account the geotextile-related products'; CEN/TC 227 on
actions on/from the structures and the 'Road materials'.
geotechnical actions; The standards on execution (TC 288) and
- EN 1998-5: Design of structures for on geotechnical tests (TC 341) are particularly
earthquake resistance. Foundations, retaining important as they complement Eurocode 7,
structures and geotechnical aspects. which is devoted only to design.

141
6 CONCLUDING REMARKS 1:2004 (E), (F) and (G), November 2004,
European Committee for Standardization:
The work for the elaboration of a common Brussels.
framework for geotechnical design throughout CEN (2006) . Eurocode 7: Geotechnical
Europe, i.e. Eurocode 7, started nearly 25 design - Part 2: Ground investigation and
years ago. Given the progress recently testing. Final draft, prEN1997-2, February
achieved, it is now sure that the corresponding 2006, European Committee for
standards/codes will be enforced soon. Standardization: Brussels.
Whatever the precise legal status of EC 7 (1990). Eurocode 7: Geotechnics.
Eurocode 7 in the various countries, it will Preliminary draft for the European
prove to be very important for the whole Communities, Geotechnik, 1990/1.
construction industry. It is meant to be a tool to Frank R. (1991 ). Quelques deweloppements
help European geotechnical engineers speak recents sur le comportement des fondations
the same technical language and also a superficielles. Rapport general, Session 3,
necessary tool for the dialogue between Comptes rendus 1Oeme Gong. Europeen
geotechnical engineers and structural Meca. Sols et Tr. Fond., Florence, 26-30
engineers. mai, vol. 3, pp. 1003-1030. (English version:
Eurocode 7 helps promote research. Some recent developments on the
Obviously, it stimulates questions on present behaviour of shallow foundations. General
geotechnical practice from ground report, Proc. 1Oth European Cont. Soil
investigation to design models. Mechs & Fdn Engng, Florence, 26-30 May,
It is our belief that it will also be very useful vol. 4, pp. 1115-1141 , 1994).
to many geotechnical and structural engineers Frank R. , Bauduin C. , Driscoll R., Kavvadas
all over the world, not only in Europe. M., Krebs Ovesen N., Orr T. , Schuppener
B. (2004 ). Designer's guide to EN 1997
REFERENCES Eurocode 7- Geotechnical design, Thomas
Telford , London , 216 pages.
Burland, J.B., Broms, B.B. and De Mello, Frank, R. & Magnan J.P. (1999). Quelques
V.F.B. (1977). Behaviour of foundations and reflexions sur Ia verification des etats limites
structures. Proc. 9th Int. Cont. Soil Mechs & ultimes suivant I'Eurocode 7 (in French - A
Fdn Engng, Tokyo 2: 495-546. few thoughts about ultimate limit states
Burland J.B. and Wroth C.P. (1975) Settlement verifications following Eurocode 7).
of buildings and associated damage, Workshop on the Eurocodes, Proc. 12th
Review Paper, Session V. Proc. Cont. European cont. soil mechs. & geot. engng,
Settlement of Structures, Cambridge: 611- 7-10 June, Amsterdam, vol. 3:2179-2183.
654. Pentech Press, London.
CEN (1994). Eurocode 7 Geotechnical design
- Part 1: General Rules. Pre-standard ENV
1997-1. European Committee for
Standardization (CEN): Brussels.
CEN (1999a). Eurocode 7 Geotechnical design
- Part 2: Geotechnical design assisted by
Laboratory Testing. Pre-standard ENV
1997-2. European Committee for
Standardization: Brussels.
CEN (1999b). Eurocode 7 Geotechnical design
- Part 3: Geotechnical design assisted by
Field Testing. Pre-standard ENV 1997-3.
European Committee for Standardization:
Brussels.
CEN (2002). Eurocode: Basis of structural
design. European standard, EN 1990 :
2002. European Committee for
Standardization: Brussels.
CEN (2004). Eurocode 7: Geotechnical
design - Part 1: General rules , EN 1997-

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